This application relates to a process for regenerating a coked catalyst comprising a zeolite and a noble metal such as platinum. The process involves treating the coked catalyst under somewhat mild oxidation conditions, whereby a sufficient portion of the coke is removed from the catalyst to restore the hydrocarbon sorption properties of the zeolite component to the level observed in the non-coked form. Surprisingly, the original activity of the catalyst, as measured in the non-coked form, is substantially restored, even though a substantial amount of coke remains on the regenerated catalyst. There is also provided herein means for monitoring the course of regenerations, as well as for mapping out conditions for subsequent regenerations.
An unwanted side reaction which often occurs in catalytic hydrocarbon conversions, especially those involving the use of catalytically active zeolites, is the formation of coke. Over time, this coke can become deposited on the zeolites in gradually increasing quantities until the activity of the catalyst is substantially reduced. When the activity of the catalyst is reduced by coke to an unsatisfactory level, it is customary to interrupt the hydrocarbon conversion process and to burn the coke off the catalyst under oxidation conditions sufficient to rapidly remove substantially all of the coke from the catalyst.
When substantially all of the coke is burned off a catalyst comprising a noble metal in combination with a zeolite, the noble metal is typically found to be in an agglomerated form. In order to fully regenerate such a catalyst, it is often necessary to subject the catalyst to further treatment, whereby the noble metal is redispersed in finely divided form to achieve maximum surface area of the noble metal on the catalyst.
Processes for redispersing noble metal on zeolite catalysts are described in U.S. Pat. Nos. 4,657,874 and 4,849,385, the entire disclosures of which are expressly incorporated herein by reference.